Electronic device and solid state imaging apparatus

ABSTRACT

Disclosed herein is an electronic device including a first electrode  21 , a second electrode  22 , and a photoelectric conversion layer  23  held between the first electrode  21  and the second electrode  22 . The first electrode  21  is formed from a transparent conductive material having a work function ranging from 5.2 to 5.9 eV, preferably from 5.5 to 5.9 eV, more preferably 5.8 to 5.9 eV.

TECHNICAL FIELD

The present disclosure relates to an electronic device and a solid stateimaging apparatus.

BACKGROUND ART

Any electronic device used as photoelectric conversion elements forimage sensors or the like is usually constructed such that onephotoelectric conversion layer is held between two electrodes. Such anelectronic device is known from JP 2014-220488A. The electronic devicedisclosed in JP 2014-220488A includes a first electrode, a secondelectrode, and a photoelectric conversion layer held between the firstand second electrodes, in which the first electrode is formed from anamorphous oxide of at least quaternary compound containing indium,gallium and/or aluminum, zinc, and oxygen, such that the secondelectrode exceeds the first electrode in work function by no smallerthan 0.4 eV. In addition, specifically, the second electrode in workfunction is larger than the first electrode in work function.

CITATION LIST Patent Literature

[PTL 1]

JP 2014-220488A

SUMMARY OF THE INVENTION Technical Problems

The electronic device disclosed in the laid-open official gazettementioned above specifies a certain value of difference in work functionbetween the second electrode and the first electrode. This difference inwork function leads to an improved internal quantum efficiency andreduced dark current when a bias voltage is applied across the first andsecond electrodes. Unfortunately, the first electrode has a workfunction ranging from 4.1 to 4.5 eV, and the second electrode has a workfunction ranging from 4.8 eV and 5.0 eV. This means that the electrodebeing configured from materials having a high work function (or thesecond electrode in the electronic device disclosed in JP 2014-220488A)is limited in selection from transparent conductive materials.Accordingly, it is necessary for the electrode to be formed from aspecies selected from a wide range of transparent conductive materials.Moreover, the electronic device is required to have outstandingcharacteristic properties, such as improved internal quantum efficiency,low specific resistance, and small dark current.

It is an object of the present disclosure to provide an electronicdevice and a solid state imaging apparatus included of such electronicdevices, the electronic device being formed from a species selected froma wide range of transparent conductive materials and having outstandingcharacteristic properties.

Solution to Problems

The electronic device according to the present disclosure which has beencompleted to achieve the foregoing object includes a first electrode, asecond electrode, and a photoelectric conversion layer held between thefirst electrode and the second electrode, in which the first electrodeis formed from a transparent conductive material having a work functionranging from 5.2 to 5.9 eV, preferably from 5.5 to 5.9 eV, morepreferably 5.8 to 5.9 eV.

The solid state imaging apparatus according to the present disclosurewhich has been completed to achieve the foregoing object includes theelectronic devices according to the present disclosure defined above.

Advantageous Effects of Invention

The electronic device disclosed herein and the electronic deviceconstituting the solid state imaging apparatus disclosed herein willcollectively referred to as “the electronic device or the like disclosedherein” herein after. The electronic device disclosed herein ischaracterized in that the first electrode is formed from a transparentconductive material having a work function ranging from 5.2 to 5.9 eV.The work function in such a range permits the second electrode to beformed from a species selected from a wide range of transparentconductive materials, so that the first and second electrodes greatlydiffer in work function from each other. This leads to the electronicdevice having outstanding characteristic properties. Incidentally, theeffects mentioned in this specification are merely exemplary and notintended to restrict the scope of the present disclosure, and it mayhave additional effects.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are schematic partial sectional views of a substrate orthe like which are intended to explain the method of producing anelectronic device according to Example 1.

FIGS. 2A and 2B are graphs representing I-V curve observed in electronicdevices according to Example 1A and Comparative Example 1, in which afirst electrode is formed from indium-cerium complex oxide and ITO,respectively.

FIGS. 3A and 3B are graphs representing spectral characteristicsobserved in the first electrode of the electronic device according toExample 1A and Comparative Example 1.

FIG. 4A is a graph depicting the result measuring relation between theamount of oxygen gas introduced (oxygen gas partial pressure) and thespecific resistance while the first electrode is formed, with the firstelectrode varying in the amount of cerium added thereto; and FIG. 4B isa graph depicting the result measuring relation between the amount oftungsten added to the first electrode and the specific resistance, whichis observed in the electronic device according to Example 1C in whichthe first electrode is formed from an indium-tungsten complex oxide.

FIG. 5A is a graph depicting the result measuring relation between theamount of oxygen gas introduced (oxygen gas partial pressure) and thelight transmission while the first electrode is formed, which isobserved in the electronic device according to Example 1C in which thefirst electrode is given tungsten added thereto in an amount of 2 atom%; and FIG. 5B is a graph depicting the result measuring relationbetween the amount of titanium added to the first electrode and thespecific resistance, which is observed in the electronic deviceaccording to Example 1D in which the first electrode is formed from anindium-titanium complex oxide.

FIG. 6 is a graph depicting spectral characteristics of the firstelectrode in the electronic device according to Example 1E andComparative Example 1.

FIGS. 7A and 7B are conceptual views depicting an energy diagram in theelectronic device according to Example 1 and Comparative Example 1; andFIGS. 7C and 7D are conceptual views depicting the correlation betweenthe difference in a work function and the energy diagram, which isobserved in the electronic device according to Example 1 and ComparativeExample 1.

FIG. 8 is a schematic view depicting a solid state imaging apparatusaccording to Example 2.

DESCRIPTION OF EMBODIMENTS

The present disclosure will be described below based on the exampleswith reference to the drawings. The disclosure mentioned herein is notintended to restrict the scope of the disclosure, and values andmaterials depicted in Examples are merely exemplary. The descriptionproceeds in the following order.

1. General description of electronic device and solid state imagingapparatus according to the present disclosure2. Example 1 (electronic device according to the present disclosure)3. Example 2 (solid state imaging apparatus according to the presentdisclosure)

4. Supplements <General Description of Electronic Device and Solid StateImaging Apparatus According to the Present Disclosure>

The electronic device or the like according to the present disclosurerelies on a transparent conductive material which is composed of indiumoxide and at least one metal species selected from a group consisting ofcerium (Ce), gallium (Ga), tungsten (W), and titanium (Ti), with themetal species accounting for 0.5 to 10 atom % of the total amount (100atom %) of the indium and the metal species. Alternatively, theelectronic device or the like according to the present disclosure relieson the transparent conductive material which is composed of indium oxideand cobalt, with the cobalt accounting for 10 to 30 atom % of the totalamount (100 atom %) of the indium and the cobalt. Here, “Addition” ofthe supplementary components includes mixing and doping.

The electronic device or the like according to the present disclosureshould preferably be embodied such that the first electrode has aspecific resistance (electrical resistance) smaller than 1×10⁻² Ω·cm andalso has a sheet resistance of 3×10 to 1×10³ Ω/□.

Furthermore, the electronic device or the like according to the presentdisclosure should preferably be embodied such that the first electrodehas a refractive index ranging from 1.9 to 2.2, so that the firstelectrode can effectively transmit light having a broad spectrumbandwidth (“transmission light spectral bandwidth”).

Furthermore, the electronic device or the like according to the presentdisclosure should preferably be embodied such that the first electrodehas surface roughness (arithmetic average roughness) Ra no larger than 1nm, so that the photoelectric conversion layer to be formed on the firstelectrode has uniform properties, which helps improve yield inproduction of the electronic device. In addition, the surface roughnessshould preferably be such that Rms (Rq: root mean square valueroughness) is no larger than 2 nm.

According to the preferred embodiment mentioned above, the electronicdevice or the like disclosed herein should have the first electrodewhose thickness ranges from 1×10⁻⁸ to 2×10⁻⁷ m, preferably 2×10⁻⁸ to1×10⁻⁷ m.

Alternatively, the electronic device or the like disclosed herein ischaracterized in that the transparent conductive material is composed ofindium oxide and cerium (Ce) [or indium-cerium complex oxide (ICO)] andthe first electrode has a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m andalso has a specific resistance no smaller than 1×10⁻³ Ω·cm and smallerthan 1×10⁻² Ω·cm. The amount of cerium should be such that cerium atomsaccount for 1 to 10 atom % in the total (100 atom %) of indium atoms andcerium atoms. Moreover, the transparent conductive material is composedof indium oxide and gallium (Ga) [or indium-gallium complex oxide(IGO)], and the first electrode has a thickness ranging from 5×10⁻⁸ to1.5×10⁻⁷ m and also has a specific resistance ranging from 1×10⁻⁵ to1×10⁻³ Ω·cm. The amount of gallium should be such that gallium atomsaccount for 1 to 30 atom %, preferably 1 to 10 atom %, in the total (100atom %) of indium atoms and gallium atoms. Furthermore, the transparentconductive material is composed of indium oxide and tungsten (W) [orindium-tungsten complex oxide (IWO)], and the first electrode has athickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m and also has a specificresistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm. The amount of tungstenshould be such that tungsten atoms account for 1 to 7 atom % in thetotal (100 atom %) of indium atoms and tungsten atoms. Moreover, thetransparent conductive material is composed of indium oxide and titanium(Ti) [or indium-titanium complex oxide (ITiO)], and the first electrodehas a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m and also has a specificresistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm. The amount of titaniumshould be such that titanium atoms account for 0.5 to 5 atom % in thetotal (100 atom %) of indium atoms and titanium atoms. Moreover, thetransparent conductive material is composed of indium oxide and cobalt(Co) [or indium-cobalt complex oxide (ICoO)], and the first electrodehas a thickness ranging from 5×10⁻³ to 2×10⁻⁷ m and also has a specificresistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm. The amount of cobaltshould be such that cobalt atoms account for 10 to 30 atom % in thetotal (100 atom %) of indium atoms and cobalt atoms. Thus, it ispossible to obtain the desired specific resistance and to enlarge thespectral bandwidth of the transmitting light by specifying the ratio ofcerium atoms, gallium atoms, tungsten atoms, titanium atoms, and cobaltatoms.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein ischaracterized in that the first and second electrodes have respectivework functions such that the subtraction of the second from the first isno smaller than 0.4 eV. The difference in work functions specified abovegenerates an internal electric field in the photoelectric conversionlayer, thereby improving the internal quantum efficiency.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein ischaracterized in that the second electrode has a work function no largerthan 5.0 eV, with the lower limit being 4.1 eV, for example.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein ischaracterized in that the second electrode is formed from indium-tincomplex oxide (ITO), indium-zinc complex oxide (IZO), or tin oxide(SnO₂). The second electrode formed from the transparent conductivematerial has a work function ranging from 4.8 to 5.0 eV, depending onfilm forming conditions. Alternatively, the second electrode may beformed from a transparent conductive material, such as gallium-zinccomplex oxide doped with indium (IGZO, In—GaZnO₄), zinc oxide doped withaluminum oxide (AZO), indium-zinc complex oxide (IZO), and zinc oxidedoped with gallium (GZO). The second electrode formed from any one ofthe transparent conductive materials mentioned above has a work functionranging from 4.1 to 4.5 eV, depending on film forming conditions.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein ischaracterized in that the first electrode is formed by the sputteringmethod. The first electrode has its transmitted light spectral bandwidthcontrolled by adjusting the amount of oxygen gas (oxygen gas partialpressure) to be introduced for sputtering. Moreover, according to thepreferred embodiment and configuration mentioned above, the electronicdevice or the like disclosed herein is characterized in that the firstelectrode contains a less amount of oxygen than the oxygen content basedon the stoichiometric composition. As the oxygen content decreases morethan the oxygen content based on the stoichiometric composition, theoxygen deficiency increases.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein ischaracterized in that the first electrode has a light transmittancepreferably, no smaller than 80% for light having a wavelength rangingfrom 400 to 660 nm. Moreover, the second electrode may have a lighttransmittance preferably, no smaller than 80% for light having awavelength ranging from 400 to 660 nm.

In addition, according to the preferred embodiment and configurationmentioned above, the electronic device or the like disclosed herein isincluded of photoelectric conversion elements.

According to the preferred embodiment and configuration mentioned above,the electronic device or the like disclosed herein is included of thesubstrate, the first electrode, the photoelectric conversion layer, andthe second electrode, which are sequentially formed one over another.Alternatively, the electronic device is included of the substrate, thesecond electrode, the photoelectric conversion layer, and the firstelectrode, which are sequentially formed one over another. In otherwords, the electronic device or the like disclosed herein is that oftwo-terminal type which has the first electrode and the secondelectrode. However, it may also be of three-terminal type, which has anadditional control electrode to control current by voltage appliedthereto. The electronic device of three-terminal type may have the samestructure as the field-effect transistor (FET), specifically, ofbottom-gate/bottom-contact type, bottom-gate/top-contact type,top-gate/bottom-contact type, or top-gate/top-contact type.Incidentally, the first electrode functions as anode (namely, to collectholes), on the other hand the second electrode functions as cathode(namely, to collect electrons). The electronic device or the like may bea multi-layered one, each having the photoelectric conversion layervarying in light absorption spectrum. Further, the electronic device orthe like may also be modified such that the substrate is formed fromsilicon semiconductor and the substrate supports thereon the drivecircuits and photoelectric conversion layer.

The photoelectric conversion layer may be an amorphous one or acrystalline one. The photoelectric conversion layer may be formed fromorganic materials such as organic semiconductor, organometal compound,organic semiconductor fine particles, metal oxide semiconductor,inorganic semiconductor fine particles, material of core-shellstructure, and organic-inorganic hybrid compound.

Examples of the organic semiconductor includes the following. Organicdyes represented by quinacridone and derivatives thereof. Alq₃[tris(8-quinolinolato)aluminum (III)], which is a dye obtained bychelating with an organic material the ion of previous period (referredto transition metal, the left side in periodic table). Organometal dyerepresented by phthalocyanine zinc (II) which is a complex compound atransition metal and an organic material. Dinaphthothienothiophene(DNTT).

Examples of the organometal compound include the following. Dye obtainedby chelating with an organic material the ion of previous periodtransition metal, which has been mentioned above. Organometal dye as acomplex formed from transition metal ion and organic material. Examplesof the organic semiconductor fine particles include the following.Associated material of organic dye represented by quinacridone andderivative thereof, mentioned above. Associated material of a dyeobtained by chelating with an organic material the ion of previousperiod transition metal. Associated material of an organometal dye incomplex form obtained from transition metal ion and organic material.Prussian blue in which metal ions are crosslinked with cyano groups, ora derivative or complex associated material thereof.

Examples of the metal oxide semiconductor and inorganic semiconductorfine particles include the following. ITO, IGZO, ZnO, IZO, IrO₂, TiO₂,SnO₂, SiO_(x), ZnO, CdTe, GaAs, Si, and metal chalcogen semiconductor(such as CdS, CdSe, ZnS, CdSe/CdS, CdSe/ZnS, and PbSe). [chalcogenincludes such elements as sulfur (S), selenium (Se), and tellurium(Te).]

Examples of the core-shell material (composed of core and coveringshells) include those of organic material (such as polystyrene andpolyaniline) and metallic material (easily or hardly ionizable).Examples of the organic-inorganic hybrid compound include coordinatepolymer, which is a generic term embracing Prussian blue and derivativesthereof in which metal ions are crosslinked with cyano groups, andothers in which metal ions are crosslinked infinitely with bipyridine orothers in which metal ions are crosslinked with multi-charged ionic acidsuch as oxalic acid and rubeanic acid.

The photoelectric conversion layer may be formed by any one of coatingmethod, physical vapor deposition (PVD) method, and chemical vapordeposition (CVD) method including MOCVD method, which are appropriatelyselected according to the material employed. Examples of the coatingmethod include spin coating; dipping; casting; printing such as screenprinting, ink jet printing, offset printing, and gravure printing;stamping; spraying; and coating such as air doctor coating, bladecoating, rod coating, knife coating, squeeze coating, reverse rollcoating, transfer roll coating, gravure coating, kis coating, castcoating, spray coating, slit orifice coating, and calender coating.Incidentally, the coating method may employ such solvent as toluene,chloroform, hexane, and ethanol, which are non-polar or weak-polarorganic solvents. In addition examples of the PVD method include vacuumvapor deposition such as electron beam heating, resistance heating, andflush deposition; plasma deposition; sputtering such as bipolarsputtering, DC sputtering, DC magnetron sputtering, high-frequencysputtering, magnetron sputtering, ion beam sputtering and biassputtering; and ion plating method such as DC (direct current) method,RF method, multicathode method, activating reaction method, electricfield vapor deposition method, high-frequency ion plating method, andreactive ion plating.

The photoelectric conversion layer is not specifically restricted inthickness; an ordinary thickness ranges from 1×10⁻¹⁰ to 5×10⁻⁷ m, forexample.

The first electrode is formed by sputtering, specifically, magnetronsputtering and parallel plate sputtering. Sputtering may be performedwith plasma generated by DC discharging or RF discharging. Incidentally,according to the present disclosure, the first electrode may have itscharacteristic properties properly controlled and improved by adjustingthe flow rate and partial pressure of oxygen gas. Thus, the firstelectrode is made to have an adequately controlled specific resistanceand an expanded spectrum range of transmitted light, for example.

The first electrode which has been formed as mentioned above mayoptionally undergo surface treatment before it is coated with thephotoelectric conversion layer. The surface treatment includesirradiation to UV light or oxygen plasma, for example. The effect of thesurface treatment is decontamination of the surface of the firstelectrode and improved adhesion between the first electrode and thephotoelectric conversion layer when the photoelectric conversion layeris formed. In addition, the surface treatment causes the first electrodeto change the state (specifically, decrease) in oxygen deficiency and toincrease in work function.

The second electrode can be formed by any one method selected from thefollowing according to the material used therefor. Sputtering methodsuch as vacuum deposition and reactive vapor deposition, PVD method suchas ion beam deposition and ion plating, pyrosol method, thermaldecomposition of organometallic compound, spraying method, dippingmethod, CVD method such as MOCVD, electroless plating method, andelectrolytic plating.

The substrate may be formed from any one of organic polymers including,for example, polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA),polyvinylphenol (PVP), polyether sulfone (PES), polyimide, polycarbonate(PC), polyethylene terephthalate (PET), and polyethylene napththalate(PEN). These polymers may be used in the form flexible film or sheet.The resulting flexible substrate leads to the electronic device that canbe built into any electronic apparatus with a curved shape.Alternatively, the substrate may also be formed from any one of thefollowing materials: glass plate with or without insulation film formedthereon, quartz plate with or without insulation film formed thereon,silicon semiconductor plate with or without insulation film formedthereon, and metal plate including that of alloy or stainless steel orthe like. Incidentally, the insulation films include those which aremade of silicon oxide (such as SiO_(x) and spin on glass (SOG)); siliconnitride (SiN_(y)), silicon oxynitride (SiON); aluminum oxide (Al₂O₃);metal oxide and metal salt. The substrate may also be a conductivesubstrate (made of metal (e.g., gold and aluminum) or highly orientedgraphite) which has its surface coated with the insulation film. Thesubstrate should preferably have a smooth surface, but slight roughnessis permissible so long as it has no adverse effect on the characteristicproperties of the photoelectric conversion layer. The substrate may haveits surface coated with a thin film (as explained below) so as toimprove adhesion between the substrate and the first electrode or thesecond electrode. The thin film for this purpose may be formed from asilanol derivative by silane coupling method, thiol derivative by SAMmethod or the like, carboxylic acid derivative, phosphoric acidderivative, or insulative metal salt or complex by CVD method or thelike.

The first electrode or the second electrode may have a coating layer,according to circumstances. The coating layer may be formed from any oneof the following materials. Inorganic insulating materials such assilicon oxide; silicon nitride (SiN_(y)); and metal oxide (e.g.,aluminum oxide (Al₂O₃)). Organic insulating materials (organic polymers)such as polymethyl methacrylate (PMMA); polyvinylphenol (PVP); polyvinylalcohol (PVA); polyimide; polycarbonate (PC), polyethylene terephthalate(PET), polystyrene, silanol derivative (e.g.,N-2(aminoethyl)3-aminopropyltrimethoxysilane (AEAPTMS),3-mercaptopropyltrimethoxysilane (MPTMS), and octadecyltrichlorosilane(OTS)), octadecane thiol, and dodecylisocyanate. These compounds arelinear hydrocarbons which have at one end functional groups capable ofbonding with the control electrode. They may be used in combination withone another.

Incidentally, the silicon oxide materials include silicon oxide(SiO_(x)), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), andSOG (spin on glass). The low-dielectric materials include polyarylether,cycloperfluorocarbon polymer, benzocyclobutene, cyclic fluororesin,polytetrafluoroethylene, fluoroaryl ether, fluoropolyamide, amorphouscarbon, and organic SOG. The insulating layer may be formed by any oneof the above-mentioned methods, such as PVD method; CVD method; spincoating method; coating method; sol-gel method; electrodepositionmethod; shadow mask method; and praying method.

The electronic device disclosed herein may be applied to not only asolid-state imaging apparatus such as TV camera but also light sensorand image sensor.

Example 1

Example 1 deals with the electronic device disclosed herein. Theelectronic device of Example 1 is illustrated in FIG. 1B which is aschematic partly sectional view.

The electronic device of Example 1 is specifically a photoelectricconversion element. It is included of a first electrode 21, a secondelectrode 22, and a photoelectric conversion layer 23 held between thefirst and second electrodes. The first electrode is formed from atransparent conductive material with a work function ranging from 5.2 to5.9 eV, preferably from 5.5 to 5.9 eV, and more preferably from 5.8 to5.9 eV. The first electrode 21, the photoelectric conversion layer 23,and the second electrode 22 are sequentially arranged on top of theother on a substrate 10 of silicon semiconductor. In other words, theelectronic device according to Example 1 is that of two-terminalstructure having the first electrode 21 and the second electrode 22.

The electronic device of Example 1 is characterized in that the firstelectrode 21 is formed from a transparent conductive material which iscomposed of indium oxide and at least one species of metal selected froma group consisting of cerium (Ce), gallium (Ga), tungsten (W), andtitanium (Ti), with the metal accounting for 0.5 to 10 atom % in thetotal amount (100 atom %) of the indium atoms and the metal atoms(Examples 1A, 1B, 1C, and 1D). Alternatively, the transparent conductivematerial is composed of indium oxide and cobalt, with the cobaltaccounting for 10 to 30 atom % in the total amount (100 atom %) of theindium atoms and the cobalt atoms (Example 1E).

To be more specific, the electronic device of Example 1 has the secondelectrode 22 formed from indium-tin complex oxide (ITO). The secondelectrode 22 is required to have a work function no larger than 5.0 eV,for example, ranging from 4.8 to 5.0 eV, with the actual value varyingdepending on the forming conditions. The first electrode 21 functions asan anode which gives off holes. The second electrode 22 functions as acathode which gives off electrons. The photoelectric conversion layer 23is a film of quinacridone in 100 μm thick.

The electronic device of Example 1 satisfies the following requirements.The first electrode 21 should have a specific resistance smaller than1×10⁻² Ω·cm, a sheet resistance ranging from 3×10 to 1×10³ Ω/□, arefractive index ranging from 1.9 to 2.2, and a thickness ranging from1×10⁻⁸ to 2×10⁻² m, preferably 2×10⁻⁸ to 1×10⁻² m. It was found that thefirst electrode with a thickness of 100 nm has a sheet resistance of 60Ω/□. The first electrode 21 should be formed by sputtering with anamount of oxygen gas to be introduced (oxygen gas partial pressure), sothat it has an adequately controlled spectral bandwidth for transmittinglight. In addition, the first electrode should contain oxygen in anamount less than the stoichiometric amount.

The first electrode 21 as well as the second electrode 22 should have alight transmittance no smaller than 80% for the wavelength ranging from400 to 660 nm. The light transmittance of the first electrode 21 and thesecond electrode 22 can be measured by observing the electrode formed ona transparent glass plate.

The electronic device of Example 1 is prepared by the process which isdescribed below with reference to FIGS. 1A and 1B.

Step-100

The first step is to get ready the substrate 10 of siliconsemiconductor, which has thereon the drive circuit (for the electronicdevice), the photoelectric conversion layer (both not depicted), awiring 11, and an insulating layer 12 (in contact with the surfacethereof). The insulating layer 12 has an opening 13 which permits thewiring 11 to expose itself at the bottom thereof. The next step is tocoat the insulating layer 12 containing the opening 13 by co-sputteringwith the first electrode 21 of the transparent conductive materialmentioned above (see FIG. 1A). Sputtering was performed by using aparallel plate sputtering apparatus or DC magnetron sputteringapparatus, argon (Ar) as the process gas, and a target of sintered bodycomposed of indium oxide and any one of cerium, gallium, tungsten,titanium, and cobalt.

Step-110

In the subsequent step, the first electrode 21 undergoes patterning andsurface treatment by irradiation with UV light. Then, the treatedsurface of the first electrode 21 is entirely coated by vacuumdeposition with the photoelectric conversion layer 23 of quinacridone.The photoelectric conversion layer 23 is further coated by sputteringwith the second electrode 22 of ITO. Sputtering was performed by using aparallel plate sputtering apparatus or DC magnetron sputteringapparatus, argon (Ar) as the process gas, and a target of sintered bodyof ITO. Thus there was obtained the electronic device of Example 1 whichhas the structure depicted in FIG. 1B.

Comparative Example 1 was carried out to produce the electronic deviceof Comparative Example 1 in the same way as Example 1 except that thefirst electrode was formed from ITO.

Each of the electronic devices of Example 1 and Comparative Example 1has the first electrode which is specified by composition, amount ofmetal added, crystallizing temperature, optical properties (refractiveindex), specific resistance, and work function, before and after surfacetreatment, as depicted in Table 1. The surface treatment by irradiationwith UV light causes the first electrode to increase in work function,which results in a large difference in work function between the firstelectrode and the second electrode. In other words, the first electrode21 and the second electrode 22 have respective work functions such thatthe subtraction of the latter from the former gives a difference nosmaller than 0.4 eV. The difference in work functions as specified aboveallows the photoelectric conversion layer 23 to generate an internalelectric field, thereby improving the internal quantum efficiency. Table1 depicts “Difference-A” which denotes the difference between the workfunction of the first electrode, before treatment, in each of Example 1and the work function of the first electrode, before treatment inComparative Example 1, and “Difference-B” which denotes the differencebetween the work function of the first electrode, after treatment ineach of Example 1 and the work function of the first electrode, aftertreatment in Comparative Example 1. Incidentally, the second electrodein each of Example 1 and Comparative Example 1 was formed from ITO andhad a work function of 4.8 eV.

TABLE 1 Examples Comp. Unit 1A 1B 1C 1D 1E Example 1 Denotation ICO IGOIWO ITiO ICiO ITO Composition In—Ce—O In—Ga—O In—W—O In—Ti—O In—Co—OIn—Sn—O Amount added Atom % 10 10 1-7 0.5 5 20 10 Crystallizing ° C. ca,300 230- 200- 150-200 150-200 230- 150-200 temperature Refractive index2.0 2.0 2.0 2.0 2.0 2.0 1.9-2.0 Specific 2 × 10⁻³ 4 × 10⁻⁴ 4 × 10⁻⁴ 2 ×10⁻⁴ 2 × 10⁻⁴ 2 × 10⁻⁴ 4 × 10⁻⁴ resistance Work function Before eV 5.75.7 5.2 5.5 5.2 5.2 4.8 Treatment After 5.8 5.9 5.8 5.8 5.9 5.8 5.0Treatment Difference - A 0.9 0.9 0.4 0.7 0.4 0.4 Difference - B 0.8 0.90.8 0.8 0.9 0.8

FIG. 2A depicts the I-V curves of light current observed in theelectronic devices (photoelectric conversion elements) of Example 1A andComparative Example 1, the former having the first electrode 21 formedfrom indium-cerium complex oxide (ICO) and the latter having the firstelectrode 21 formed from ITO. The curves “A” and “B,” each representsthe results in Example 1A and Comparative Example 1 throughout the FIGS.2A, 2B, 3A, and 3B. It is noted from FIG. 2A that the electronic deviceof Example 1A steeply increases in current upon application of a reversebias voltage slightly lower than 1 volt (or a bias voltage slightlylower than −1 volt). Also, it gives a dark current as indicated by theI-V curve in FIG. 2B. It is noted that the dark current in ComparativeExample 1 is 2×10⁻⁹ A/cm² at a bias voltage of −3 volt, whereas the darkcurrent in Example 1A is as low as 6×10⁻¹¹ A/cm² under the sameconditions.

Furthermore, the electronic devices of Example 1A and ComparativeExample 1 is found to have the internal quantum efficiency as depictedin Table 2 below. The internal quantum efficiency η denotes the ratio ofthe number of incident photons to the number of emitted electrons. It isrepresented by the equation below. Table 2 also depicts the measurementresult of the surface roughness of the first electrode. It is noted thatthere is a difference (lager than an order of magnitude) between Example1A and Comparative Example 1. The first electrode 21 of Example 1 has asurface roughness (arithmetic mean roughness) Ra no larger than 1 nm anda surface roughness Rms no larger than 2 nm.

η={(h·c)/(q*λ)}(I/P)=(1.24/Δ)(I/P)

where,h: Planck constantc: light velocityq: charge of electronΔ: wavelength of incident light (μm)I: light current (A/cm²) at 1 V of reverse voltage (in measurements forExample 1)P: power of incident light (A/cm²)

TABLE 2 Internal quantum efficiency Ra Rms (%) (nm) (nm) Example 1A 800.36 0.46 Comparative 68 2.5 3.6 Example 1

The electronic device of Comparative Example 1 has the first electrodeand the second electrode which are both formed from ITO. Thus, they haveno difference between their work functions Eφ₁ and Eφ₂, as depicted inFIG. 7B which is a schematic energy diagram. The result is that holeseasily flow into the second electrode, thereby increasing the darkcurrent. The fact that the first electrode and the second electrode haveno difference between their work functions Eφ₁ and Eφ₂ leads to theabsence of potential gradient (or the absence of the internal electricfield in the photoelectric conversion layer) in releasing electrons andholes, which prevents the smooth release of electrons and holes (seeconceptual view in FIG. 7D). By contrast, the electronic device ofExample 1A has the first electrode, which is formed from a transparentconductive material composed of indium oxide and cerium (Ce) addedthereto, and the second electrode, which is formed from ITO. Therefore,the first electrode has a work function Eφ₁ and the second electrode hasa work function Eφ₂ such that the difference (Eφ₁ minus Eφ₂) is nosmaller than 0.4 eV. This is illustrated by the energy diagram in FIG.7A. This produces the effect of preventing holes from entering thesecond electrode, thereby suppressing dark current. The fact that thefirst electrode has a work function Eφ₁ and the second electrode has awork function Eφ₂ such that the difference (Eφ₁ minus Eφ₂) is no smallerthan 0.4 eV leads to the presence of the potential gradient (or thepresence of the internal electric field in the photoelectric conversionlayer) in releasing electrons and holes, which permits the smoothrelease of electrons and holes (see conceptual view in FIG. 7C).

Each of the first electrodes in the electronic devices of Example 1A andComparative Example 1 has the spectral characteristics as depicted inFIGS. 3A (for light transmittance) and 3B (for light absorptivity).Incidentally, the first electrode 21 in Example 1A has a ceriumconcentration of 10 atom % and a film thickness of 150 nm, whereas thefirst electrode in Comparative Example 1 has a film thickness of 150 nm.It is noted from FIGS. 3A and 3B that the electronic devices of Example1A and Comparative Example 1 are almost the same in spectralcharacteristics.

The first electrode in the electronic device of Example 1A varies in therelation between the amount of oxygen gas (oxygen gas partial pressure)to be introduced to form the first electrode and the specific resistanceof the first electrode, the relation depending on the concentration ofcerium added to the first electrode, as depicted in FIG. 4A. The curve“A” in FIG. 4A denoted with the amount of cerium added adjusted to 10atom %, the specific resistance was smaller than 1×10⁻² Ω·cm in 1% ofoxygen gas partial pressure. On the other hand, the curves “B” and “C”in FIG. 4A denoted with the amount of cerium added adjusted to 20 atom %and 30 atom %, respectively, the specific resistance was exceeded 1×10⁻²Ω·cm.

The electronic device of Example 1C has the first electrode 21 which isformed from indium-tungsten complex oxide. The first electrode 21 gavethe specific resistance which varies depending on the amount of tungstenadded as depicted in FIG. 4B. It is noted that the first electrode has aspecific resistance no higher than 1×10⁻³ Ω·cm in the case where theamount of tungsten added is 1 to 7 atom %.

The first electrode in the electronic device of Example 1C varies in therelation between the amount of oxygen gas (oxygen gas partial pressure)to be introduced to form the first electrode and the light transmittanceof the first electrode, with the amount of tungsten added to the firstelectrode kept at 2 atom %, as depicted in FIG. 5A. In addition,experiments were carried out in which the partial pressure of oxygen gassupplied to form the film was adjusted to 0.5%, 1.0%, 1.5%, and 2.0%. Itwas found that the sample with the oxygen gas partial pressure higherthan 1% gave an average visible light transmittance of 82% inComparative Example 1 and 84% in Example 1C. In other words, the lighttransmittance is almost the same in both Example 1C and ComparativeExample 1.

The electronic device of Example 1B has the first electrode 21 which isformed from indium-gallium complex oxide. The first electrode 21 gavethe specific resistance which varies depending on the amount of galliumadded as depicted in Table 3 below. It is noted that the first electrodekeeps a specific resistance of 1×10⁻³ Ω·cm in the case where the amountof gallium added is up to 30 atom %. Incidentally, the specificresistance of ITO (Sn: 10 atom %) was 1×10⁻⁴ Ω·cm.

TABLE 3 Amount of gallium added Specific resistance (atom %) (Ω · cm) 104.5 × 10⁻⁴ 20 7.1 × 10⁻⁴ 30 1.2 × 10⁻³ 40 2.8 × 10⁻³

The electronic device of Example 1D has the first electrode 21 which isformed from indium-titanium complex oxide. The first electrode 21 gavethe specific resistance which varies depending on the amount of titaniumadded as depicted in FIG. 5B. It is noted that the specific resistanceis 1×10⁻³ Ω/cm in the case where the amount of titanium added is nolarger than 4 atom % if the film-forming step is carried out at roomtemperature (RT). It is also noted that the specific resistance is1×10⁻³ Ω/cm in the case where the amount of titanium added is no largerthan 5 atom % even though the film-forming step is carried out at 300°C.

The electronic devices of Example 1E and Comparative Example 1 each hasthe first electrode which gives the spectral characteristics depicted inFIG. 6. The upper and lower parts of FIG. 6 depict the lighttransmittance and the light absorptivity, respectively. Incidentally,the electronic device of Example 1E has the first electrode 21 whichcontains 20 atom % of cobalt added and has a thickness of 50 nm. Also,the electronic device of Comparative Example 1 has the first electrodewhich has a thickness of 150 nm. In FIG. 6, the curves “A” and “B”represent respectively the data for Example 1A and the data forComparative Example 1. It is noted that the sample of Example 1A is muchhigher than the sample of Comparative Example 1 in light absorptivityfor light with a wavelength no larger than 400 nm. This offers anadvantage that the electronic device may have another electronic deviceadded to the lower side thereof, without the lower member being exposedto much UV light. Also, experiments were carried out in which theelectronic device of Example 1E was prepared, with the amount of cobaltchanged to 10 atom %, 20 atom %, or 30 atom %. The resulting sampleswere examined to see how the first electrode changes in work functionafter surface treatment with UV light irradiation. The results aredepicted in Table 4. It was found that the work function does notappreciably change regardless of the amount of cobalt added.

Light absorptivity at Light absorptivity at wavelength of 400 nmwavelength of 350 nm Example 1E 5.7%  22% Comparative 1.5% 2.4% Example1

TABLE 4 Amount of Work function Work function cobalt added (beforesurface treatment) (after surface treatment) 10 atom % 5.1 eV 5.8 eV 20atom % 5.2 eV 5.8 eV 30 atom % 5.1 eV 5.8 eV

The results mentioned above and the results obtained from variousexperiments suggest that the transparent conductive material shouldpreferably be formed from indium-cerium complex oxide (ICO) composed ofindium oxide and cerium added thereto, and the first electrode 21 shouldpreferably have a thickness of 5×10⁻⁸ to 2×10⁻⁷ m and a specificresistance no smaller than 1×10⁻³ Ω·cm and smaller than 1×10⁻² Ω·cm. Theamount of cerium added should preferably be 1 to 10 atom %.Alternatively, the transparent conductive material should preferably beformed from indium-gallium complex oxide (IGO) composed of indium oxideand gallium added thereto, and the first electrode 21 should preferablyhave a thickness of 5×10⁻⁸ to 1.5×10⁻⁷ m and a specific resistance from1×10⁻⁵ to 1×10⁻³ Ω·cm. The amount of gallium added should be 1 to 30atom %, desirably be 1 to 10 atom %. Furthermore, the transparentconductive material should preferably be formed from indium-tungstencomplex oxide (IWO) composed of indium oxide and tungsten added thereto,and the first electrode 21 should preferably have a thickness of 5×10⁻⁸to 2×10⁻⁷ m and a specific resistance from 1×10⁻⁴ to 1×10⁻³ Ω·cm. Theamount of tungsten added should be 1 to 7 atom %. Furthermore, thetransparent conductive material should preferably be formed fromindium-titanium complex oxide (ITiO) composed of indium oxide andtitanium added thereto, and the first electrode 21 should preferablyhave a thickness of 5×10⁻⁸ to 2×10⁻⁷ m and a specific resistance from1×10⁻⁴ to 1×10⁻³ Ω·cm. The amount of titanium added should preferably be0.5 to 5 atom %. Furthermore, the transparent conductive material shouldpreferably be formed from indium-cobalt complex oxide (ICoO) composed ofindium oxide and cobalt added thereto, and the first electrode 21 shouldpreferably have a thickness of 5×10⁻⁸ to 2×10⁻⁷ m and a specificresistance from 1×10⁻⁴ to 1×10⁻³ Ω·cm. The amount of cobalt added shouldpreferably be 10 to 30 atom %.

The electronic device in which the second electrode 22 is formed fromITO will be obtained from the electronic device in which the secondelectrode 22 is formed from any one of indium-zinc complex oxide (IZO),tin oxide (SnO₂), indium-doped gallium-zinc complex oxide (IGZO,InGaZnO₄), aluminum oxide-doped zinc oxide (AZO), indium-zinc complexoxide (IZO), and gallium-doped zinc oxide (GZO) will also functionsubstantially in the same way as the electronic device of Example 1 inwhich the second electrode 22 is formed from ITO.

The fact that the electronic device of Example 1 has the first electrodewhich is made of a transparent conductive material with a work functionranging from 5.2 to 5.9 eV, as mentioned above, results in a largedifference in work functions between the first electrode and the secondelectrode. This makes it possible to form the second electrode from anyone selected from a wide range of transparent conductive materials,which leads to the production of an electronic device having superiorcharacteristic properties. Moreover, the first and second electrodeshaving the specific work functions mentioned above cause thephotoelectric conversion layer to generate a large internal electricfield when a bias voltage (or a reverse bias voltage) is applied acrossthem. This improves the internal quantum efficiency and increases thephotoelectric current while suppressing dark current.

Example 2

Example 2 is concerned with the solid state imaging apparatus accordingto the present disclosure. The solid state imaging apparatus of Example2 is provided with the electronic devices (or photoelectric conversionelements) of Example 1.

The solid state imaging apparatus (or solid state imaging element) ofExample 2 is schematically depicted in FIG. 8. A solid state imagingapparatus 40 of Example 2 is included of the semiconductor substrate (orsilicon semiconductor substrate) and an imaging region 41 formed thereonwhich has electronic devices (photoelectric conversion elements) 30described in Example 1, which are arranged in a pattern oftwo-dimensional array. The solid state imaging apparatus 40 also hasperipheral circuits such as vertical drive circuits 42, column signalprocessing circuits 43, horizontal drive circuits 44, and controlcircuits 46. These circuits may be formed from any known ones. Thecircuit structure is not limited to the one mentioned above; it will bepossible to use various circuits used for the existing CCD or CMOSimaging apparatus.

The control circuit 46 generates the clock signals and control signals(in response to vertical synchronous signals, horizontal synchronoussignals, and master clock) which function as the standard for action ofthe vertical drive circuits 42, the column signal processing circuits43, the horizontal drive circuits 44. The thus generated clock signalsand control signals are put into the vertical drive circuits 42, thecolumn signal processing circuits 43, and the horizontal drive circuits44.

The vertical drive circuits 42 are included of shift registers or thelike. It selects and scans the electronic devices 30 in the imagingregion 41 row by row in the vertical direction. Each of the electronicdevices 30 generates the pixel signal in response to the current(signal) which has been generated in proportion to the amount ofincident light. The pixel signal is sent to the column signal processingcircuit 43 through a vertical signal line 47.

The column signal processing circuits 43 are arranged for each column inthe electronic device 30. They process the signals from the electronicdevices 30 in one column, thereby removing noise and amplifying signals.This signal processing is based on the signal from the black referencepixel (formed around the effective pixel region, not depicted). Thecolumn signal processing circuit 43 has the output stage in which thehorizontal selection switch (not depicted) is connected to a horizontalsignal line 48.

The horizontal drive circuits 44 are included of the shift registers.They output the horizontal scanning pulses sequentially, therebyselecting the column signal processing circuits 43 sequentially andcausing the column signal processing circuits 43 to send signals to thehorizontal signal line 48.

An output circuit 45 processes the signals which are sequentiallysupplied thorough the horizontal signal line 48 from the column signalprocessing circuit 43.

The photoelectric conversion layer may be constructed such that itfunctions as the color filter by itself if it is formed from anappropriate material. In this case, the color filter is not necessaryfor color separation. However, if necessary, the electronic device 30has its upper surface (for the incident light) coated with any knowncolor filter that transmits light of specific wavelength such as red,green, blue, cyan, magenta, and yellow. In addition, the solid stateimaging apparatus may be of front irradiation type or of rearirradiation type. Moreover, if necessary, the electronic device 30 maybe provided with a shutter to control the amount of incident light.

The present disclosure has been described above with reference to thepreferred embodiment. However, the present disclosure is not restrictedto the embodiments mentioned above. The electronic device (photoelectricconversion element) and the solid state imaging apparatus which havebeen explained in Examples are based on the structure, configuration,manufacturing conditions, manufacturing process, and materials to beused specified above; however, they are merely exemplary and they may beproperly changed according to need. The electronic device according tothe present disclosure may be used as the solar cell. In this case, thephotoelectric conversion layer should be exposed to sunlight withoutvoltage applied across the first electrode and the second electrode. Inaddition, the electronic device according to the present disclosure mayfind use for optical sensors and image sensors in addition to theimaging apparatus (solid state imaging apparatus) such as TV cameras.

The present disclosure disclosed herein may be variously modified asfollows.

[A01]<<Electronic Device>>

An electronic device including a first electrode, a second electrode,and a photoelectric conversion layer held between the first electrodeand the second electrode, in which the first electrode is formed from atransparent conductive material having a work function ranging from 5.2to 5.9 eV.

[A02] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and at leastone metal species selected from a group consisting of cerium, gallium,tungsten, and titanium, with the metal species accounting for 0.5 to 10atom % of the total amount (100 atom %) of the indium and the metalspecies.

[A03] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and cobalt,with the cobalt accounting for 10 to 30 atom % of the total amount (100atom %) of indium and cobalt.

[A04] The electronic device as defined in any one of [A01] to [A03], inwhich the first electrode has a specific resistance smaller than 1×10⁻²Ω·cm.

[A05] The electronic device as defined in any one of [A01] to [A04], inwhich the first electrode has a sheet resistance of 3×10 to 1×10³ Ω/□.

[A06] The electronic device as defined in any one of [A01] to [A05], inwhich the first electrode has a refractive index of 1.9 to 2.2.

[A07] The electronic device as defined in any one of [A01] to [A06], inwhich the first electrode has a surface roughness Ra no larger than 1nm.

[A08] The electronic device as defined in [A07], in which the firstelectrode has a surface roughness Rms no larger than 2 nm.

[A09] The electronic device as defined in any one of [A01] to [A08], inwhich the first electrode has a thickness ranging from 1×10⁻⁸ to 2×10⁻⁷m.

[A10] The electronic device as defined in [A09], in which the firstelectrode has a thickness ranging from 2×10⁻⁸ to 1×10⁻⁷ m.

[A11] The electronic device as defined in [A01], in which thetransparent conductive material is formed from a material composed ofindium oxide and cerium added thereto, and the first electrode has athickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m and a specific resistance nosmaller than 1×10⁻³ Ω·cm and smaller than 1×10⁻² Ω·cm.

[A12] The electronic device as defined in [A11], in which ceriumaccounts for 1 to 10 atom % of the total amount (100 atom %) of indiumand cerium.

[A13] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and galliumadded thereto, and the first electrode has a thickness ranging from5×10⁻⁸ to 1.5×10⁻⁷ m and a specific resistance ranging from 1×10⁻⁵ to1×10⁻³ Ω·cm.

[A14] The electronic device as defined in [A13], in which the galliumaccounts for 1 to 30 atom %, preferably 1 to 10 atom %, of the totalamount (100 atom %) of indium and gallium.

[A15] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and tungstenadded thereto, and

the first electrode has a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m anda specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.

[A16] The electronic device as defined in [A15], in which the tungstenaccounts for 1 to 7 atom % of the total amount (100 atom %) of indiumand tungsten.

[A17] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and titaniumadded thereto, and

the first electrode has a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m anda specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.

[A18] The electronic device as defined in [A17], in which the titaniumaccounts for 0.5 to 5 atom % of the total amount (100 atom %) of indiumand titanium.

[A19] The electronic device as defined in [A01], in which thetransparent conductive material is composed of indium oxide and cobaltadded thereto, and

the first electrode has a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m anda specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.

[A20] The electronic device as defined in [A19], in which the cobaltaccounts for 10 to 30 atom % of the total amount (100 atom %) of indiumand cobalt.

[A21] The electronic device as defined in any one of [A01] to [A20], inwhich the first electrode and the second electrode have respective workfunctions such that the subtraction of the second from the first is nosmaller than 0.4 eV.

[A22] The electronic device as defined in any one of [A01] to [A21], inwhich the first electrode and the second electrode have respective workfunctions such that the subtraction of the second from the first is nosmaller than 0.4 eV, so that the difference in work function causes thephotoelectric conversion layer to generate an internal electric field,thereby improving an internal quantum efficiency.

[A23] The electronic device as defined in any one of [A01] to [A22], inwhich the second electrode has a work function no larger than 5.0 eV.

[A24] The electronic device as defined in any one of [A01] to [A23], inwhich the second electrode is formed from indium-tin complex oxide,indium-zinc complex oxide, or tin oxide.

[A25] The electronic device as defined in any one of [A01] to [A23], inwhich the second electrode is formed from indium-doped gallium-zinccomplex oxide, aluminum oxide-doped zinc oxide, indium-zinc complexoxide, or gallium-doped zinc oxide.

[A26] The electronic device as defined in any one of [A01] to [A25], inwhich the first electrode is formed by sputtering.

[A27] The electronic device as defined in [A26], in which the firstelectrode has the spectral bandwidth of transmitting light controlled byadjusting the amount of oxygen gas introduced to form the firstelectrode by sputtering.

[A28] The electronic device as defined in any one of [A01] to [A25], inwhich the first electrode contains oxygen in an amount less than thestoichiometric content.

[A29] The electronic device as defined in any one of [A01] to [A28],which is included of the substrate, the first electrode, thephotoelectric conversion layer, and the second layer which are arrangedsequentially top on the other.

[B01]<<Solid state imaging apparatus>>

A solid state imaging apparatus which has the electronic devices definedin any one of [A01] to [A29].

REFERENCE SIGNS LIST

-   10 . . . Substrate-   11 . . . Wiring-   12 . . . Insulating layer-   13 . . . Opening-   21 . . . First electrode-   22 . . . Second electrode-   23 . . . Photoelectric conversion layer-   30 . . . Electronic device (photoelectric conversion element)-   40 . . . Solid state imaging apparatus-   41 . . . Imaging region-   42 . . . Vertical drive circuits-   43 . . . Column signal processing circuits-   44 . . . Horizontal drive circuits-   45 . . . Output circuit-   46 . . . Control circuits-   47 . . . Vertical signal line-   48 . . . Horizontal signal line

1. An electronic device comprising a first electrode, a secondelectrode, and a photoelectric conversion layer held between the firstelectrode and the second electrode, wherein the first electrode isformed from a transparent conductive material having a work functionranging from 5.2 to 5.9 eV.
 2. The electronic device as defined in claim1, wherein the transparent conductive material is composed of indiumoxide and at least one metal species selected from a group consisting ofcerium, gallium, tungsten, and titanium, with the metal speciesaccounting for 0.5 to 10 atom % of the total amount, 100 atom %, of theindium and the metal species.
 3. The electronic device as defined inclaim 1, wherein the transparent conductive material is composed ofindium oxide and cobalt, with the cobalt accounting for 10 to 30 atom %of the total amount, 100 atom %, of indium and cobalt.
 4. The electronicdevice as defined in claim 1, wherein the first electrode has a specificresistance smaller than 1×10⁻² Ω·cm.
 5. The electronic device as definedin claim 1, wherein the first electrode has a refractive index of 1.9 to2.2.
 6. The electronic device as defined in claim 1, wherein the firstelectrode has a surface roughness Ra no larger than 1 nm.
 7. Theelectronic device as defined in claim 1, wherein the first electrode hasa thickness ranging from 1×10⁻⁸ to 2×10⁻⁷ m.
 8. The electronic device asdefined in claim 7, wherein the first electrode has a thickness rangingfrom 2×10⁻⁸ to 1×10⁻⁷ m.
 9. The electronic device as defined in claim 1,wherein the transparent conductive material is formed from a materialcomposed of indium oxide and cerium added thereto, and the firstelectrode has a thickness ranging from 5×10⁻⁸ to 2×10⁻⁷ m and a specificresistance no smaller than 1×10⁻³ Ω·cm and smaller than 1×10⁻² Ω·cm. 10.The electronic device as defined in claim 1, wherein the transparentconductive material is composed of indium oxide and gallium addedthereto, and the first electrode has a thickness ranging from 5×10⁻⁸ to1.5×10⁻⁷ m and a specific resistance ranging from 1×10⁻⁵ to 1×10⁻³ Ω·cm.11. The electronic device as defined in claim 1, wherein the transparentconductive material is composed of indium oxide and tungsten addedthereto, and the first electrode has a thickness ranging from 5×10⁻⁸ to2×10⁻⁷ m and a specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.12. The electronic device as defined in claim 1, wherein the transparentconductive material is composed of indium oxide and titanium addedthereto, and the first electrode has a thickness ranging from 5×10⁻⁸ to2×10⁻⁷ m and a specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.13. The electronic device as defined in claim 1, wherein the transparentconductive material is composed of indium oxide and cobalt addedthereto, and the first electrode has a thickness ranging from 5×10⁻⁸ to2×10⁻⁷ m and a specific resistance ranging from 1×10⁻⁴ to 1×10⁻³ Ω·cm.14. The electronic device as defined in claim 1, wherein the firstelectrode and the second electrode have respective work functions suchthat the subtraction of the second from the first is no smaller than 0.4eV.
 15. The electronic device as defined in claim 1, wherein the firstelectrode and the second electrode have respective work functions suchthat the subtraction of the second from the first is no smaller than 0.4eV, so that the difference in work function causes the photoelectricconversion layer to generate an internal electric field, therebyimproving an internal quantum efficiency.
 16. The electronic device asdefined in claim 1, wherein the second electrode has a work function nolarger than 5.0 eV.
 17. The electronic device as defined in claim 1,wherein the second electrode is formed from indium-tin complex oxide,indium-zinc complex oxide, or tin oxide.
 18. The electronic device asdefined in claim 1, wherein the first electrode contains oxygen in anamount less than a stoichiometric content.
 19. A solid state imagingapparatus which has the electronic devices defined in claim 1.